The present invention refers to a pneumatic seed distributor, which is vacuum operated (by suctionxe2x80x94negative pressure) and to be mounted to a sowing agricultural implement, particularly a sowing agricultural device used for planting seeds with low mass and reduced dimensions, such as some horticultural seeds, either bare or coated.
There are known in the art the pneumatic distributors comprising a casing with a substantially cylindrical shape, in whose inside is rotatably mounted, to a horizontal shaft, usually coaxial to the cylinder axis, a flat disc, usually provided with a concentric row of circumferentially spaced holes, whose cross section is smaller than that of the seeds to be planted. The rotating disc divides the casing, medianly, in a seed chamber, which receives the seeds coming from a feeding reservoir mounted to the agricultural implement, and in a suction chamber, which is maintained in fluid communication with a vacuum source dimensioned to draw the air from the inside of the suction chamber, causing a depression inside the latter in relation to the seed chamber, and making the seeds of the seed chamber, which are submitted to a certain angular displacement by actuation of an agitating means incorporated to the disc, be retained against the holes until they reach, with the angular rotation of the disc, a discharge chamber, from which the seeds, no more subjected to the pressure differential between the seed chamber and the suction chamber, are released from the holes and fall by gravity towards the soil.
In these pneumatic distributors, each hole of the disc commonly receives and retains, upon passing by the lower portion of the seed chamber, more than one seed, avoiding the distribution of the seeds onto the soil to occur in a uniform way, which is necessary to efficiently use the seeds, as a function of the sown area. The inadequate distribution of the seeds may easily reach a level which makes the productivity of the sown plants economically unacceptable, or which results in a final product not complying with the physical patterns required by the market.
Aiming at minimizing the operational problem cited above, the known pneumatic distributors are provided, inside the casing, with a seed selecting device, which acts on the row of holes, to promote the withdrawal of the excess seeds from the holes and therefore permit an adequate and uniform distribution of the seeds onto the soil.
To allow the same disc to operate adequately with different average patterns of seeds of a determined type, the selecting device is selectively adjustable from the outside of the casing, so as to act more or less intensively on the row of holes, guaranteeing the maintenance of only one seed in each hole. The adjustment of the interfering positioning of the selective device with the row of holes will depend on the physical characteristics of the seeds being planted.
It is also known in the art the provision, in the suction chamber, of an air intake, provided with an adjustment means, in order to obtain the adjustment of the pressure differential between the chambers and, consequently, of the pneumatic force that retains the seeds in the holes of the disc, as a function of the dimensions and of the density of the seeds being planted.
The adjustment of the position of the selector and of the intensity of the sub-pressure in the suction chamber allows the adjustment of the distributing device for each seed pattern, assuring the desired sowing uniformity, with each hole usually releasing only one seed.
Brazilian Patent PI 9404952, corresponding to the French Patent 2713436 and to U.S. Pat. No. 5,535,917, describes and claims a pneumatic distributor of the type considered herein, but having a disc with multiple concentric rows of holes and a selecting device, acting solely on one of the end rows of holes, so that the excess seeds, which are extracted from said row of holes, provoke the withdrawal of the excess seeds from the other rows of holes which are not subjected to the direct action of the selecting device.
According to the specification of this prior patent, the multiple concentric rows of holes with the adequate an predetermined actuation of a selector on one of the rows allows a higher density in the distribution of seeds to be simultaneously obtained, by using only one selector and obtaining the liberation of only one seed corresponding to each hole, by means of a relatively low rotational speed of the disc.
As mentioned in this prior art document, the solution described and claimed therein is designed to the sowing of seeds under a high density regimen, such as those from soy-bean, sorghum, sunflower, cotton, beans, etc., and with a high sowing speed. In this example, as well as in other cereal cultures, the seeds have a critical mass, which makes impossible, at least in theory, to obtain the xe2x80x9cindirect selectingxe2x80x9d effect disclosed in PI 9404952-1. According to this effect, the excess seeds, extracted from a row of holes by the selector, hit the excess seeds of the adjacent row, removing them from the holes.
This type of seed selection proposed by the prior art has, among others, the serious inconvenience of being totally infeasible to promote the discharge of the excess seeds when horticultural seeds are concerned, since these seeds invariably have small dimensions, different densities and are very light, not having enough mass to provoke said indirect selecting effect. The use of this known solution in the horticultural field would result in a disordered planting.
Besides the inconvenience cited above, it should be further observed that the prior art has a discharge device, which collects the seeds from soy-bean, sorghum, sunflower, cotton, beans and from other agricultural products, pneumatically liberated from the holes, and conducting them to the soil through a single duct. With this known arrangement, the planting is obtained in only one alignment, with the seeds being mutually spaced as a function of the rotational speed imparted to the disc and of the number of holes. But, in the case of some horticultural products, such as carrot, onion, beetroot, radish and the like, the product to be commercialized should be within average dimensional patterns highly desired by the market. These products of a desired size sell better, being therefore, more competitive. Since these products are sown in a single alignment, they tend to assume dimensions not complying with the desired patterns, and they usually reach larger sizes, as their plants develop with no laterally adjacent competing plants, which function as mutual controllers of the growth of the products, avoiding, with a relative positioning between the seeds, that very large or very small bulbs are picked up.
Still another aspect of the known pneumatic distributors relates to keeping the holes in the operational condition during the sowing operation. In this devices, it is not rare to happen that a seed of smaller dimensions or any kind of debris be stuck inside a hole, even when the latter is passing by the seed discharge region, from which the seeds, in an angular displacement, leave the suction chamber. The prior art devices do not have a pneumatic cleaning device to ensure the cleaning of the holes just after the seeds are discharged.
It is an objective of the present invention to provide a pneumatic distributor of horticultural seeds, which is vacuum operated and to be mounted to a sowing agricultural implement and which permits to obtain a uniform sowing of different patterns of seeds with small dimensions and reduced mass, on multiple rows, with the seeds of one row being offset in relation to the seeds of the adjacent row.
It is a further objective of this invention to provide a distributor of the type mentioned above and which has a self-cleaning pneumatic device for its seed selecting means.
The objectives above are attained by the provision of a distributor of horticultural seeds for a sowing agricultural implement, conventionally comprising a casing and a disc rotatably mounted inside the casing, dividing the latter into a seed chamber and in a suction chamber maintained in fluid communication with a suction device and selectively and adjustably connected to the atmosphere, said disc having, in a concentric circular arrangement, at least two rows of mutually spaced holes, said casing having a discharge chamber, inside which is provided a certain circumferential extension of the rows of holes subjected only to the atmospheric pressure of the seed chamber.
According to the invention, the distributor comprises, for each row of holes, a selector mounted inside the casing, adjacent to the face of the disc turned to the seed chamber and having a leading edge extension, which is selectively displaceable, in order to interfere, upon rotation of the disc, with the path of a predetermined part of the seeds which are pneumatically carried in each hole of the respective row of holes, so that each hole enters the discharge chamber carrying a desired number of seeds, the discharge chamber being inferiorly opened to discharge channels defined between the casing and the face of the disc turned to the seed chamber, each discharge channel being arranged in such a way as to receive the seeds released from a respective row of holes, when they enter the discharge chamber and to direct them to a descending duct, inferiorly opened to a respective soil furrower, which is longitudinally disaligned in relation to the other furrowers.
The construction defined above allows, not only the known adjustment of the intensity of the pneumatic force that retains the seeds in the holes of the disc, making it adequate to the mass of the seeds being planted, but also a precise adjustment of the level of interference that each selector in the respective row of holes, ensuring the uniform supply of a certain number of seeds, preferably one seed in the case of bare seeds, for each hole reaching the discharge chamber upon rotation of the disc and providing the sowing of multiple rows of seeds, each row corresponding to a soil furrower of the sowing device, thus forming a double line of seeds on the soil, spaced from each other. Thus, it is achieved a sowing arrangement with characteristics not provided by the solutions known heretofore and which may be further developed with the holes of the adjacent rows of holes being angularly offset.